Tyre Tread Depth: The UK Legal Limit and How to Check Yours

The legal limit

In the UK, car tyres must have at least 1.6mm of tread across the central three-quarters of the tread width, around the whole circumference of the tyre. Below that, the tyre is illegal.

Driving on illegal tyres can mean a fine of up to £2,500 and three penalty points per tyre, and an illegal tyre is an MOT fail.

Why 1.6mm is not the whole story

Tread clears water from under the tyre so the rubber stays in contact with the road. As tread depth falls, the tyre clears less water, and braking distances in the wet increase noticeably, well before you reach the legal limit.

That is why many drivers, and many tyre makers, suggest changing tyres at around 3mm, particularly before winter.

How to check your tread

Most tyres have tread wear indicators, small raised bars in the bottom of the main grooves. When the tread is level with them, the tyre is at the legal limit.

The 20p test is a quick guide: put a 20p coin into the main groove. If you can see the outer band of the coin, the tread may be close to or below the limit and should be checked properly. Check in several places on each tyre, including the inner edge.

Uneven wear tells a story

Wear on one edge usually points to tracking or suspension problems. Wear down the middle can mean over-inflation, and wear on both edges can mean under-inflation. If your tyres wear unevenly, replacing them without fixing the cause means the new ones will go the same way.

Tyres and tracking in Oldbury

We supply and fit tyres and check wheel alignment at our workshop on Park Lane in Oldbury. If you are not sure whether your tyres are legal, call us on 0121 544 3736 and we will check them for you.